Rather than choose an anonymous Green Lantern, the individual in question should be Abin Sur, the Corps’ protector of Sector 2814, which includes Earth.
While many fans have been speculating that this “key sequence” will be one of the prominent human Green Lanterns, like Hal Jordan or John Stewart, cameoing perhaps towards the end of the movie, we’ve speculated that a non-human Green Lantern might intercept Steppenwolf and his forces on his way to Earth at the beginning of the movie.
His demise means that sector will need a new protector, thus paving the way for Hal Jordan’s introduction.
The primary conflict in Justice League will revolve around the superhero team fighting Steppenwolf, who has come to Earth with his Parademon army in search of the three Mother Boxes.